This Instructable was written by Mark Thuelund Ottesen and Martin Fahlgren Larsen, from UCL Odense, Denmark as part of our Arduino project.
We wanted to make a device that could be used to suck away the unpleasant fumes when soldering. The solution we came up with was a simple box with two PC PWM fans to suck in the air through a carbon filter sheet, that would filter the air to a degree.
The Arduino can control the fan speed by turning the potentiometer on the front of the box. Only the speed of the large fan can be controlled this way. The smaller fan on the back simply turns on when the large fan reaches a speed of 50% or higher. This way the unit is fairly quiet at lower speeds and if needed serious airflow is not a problem at high speeds.
We originally planned to add an OLED screen to the front of the unit, one that would display the speed of the fans, but also indicate that the unit was on. Unfortunately the OLED panel we ordered on eBay never arrived in time to us to implement it properly in the project.
We do still have printing of the fan speed to the serial communication as a proof of concept though.
Total parts needed:
Arduino (Any will do, but keep in mind that not all Arduinos can be supplied with 12V like the Uno!)
92mm PWM fan
80mm PWM fan
10k linear potentiometer
A sheet of 8mm carbon filter
A large sheet of 4mm wood (or similar) for lasercutting
Various DC plugs and jacks
Step 1: Building the Circuit and Writing the Code
Our circuit is powered by a single 12V wall power supply. This is ideal as the fans run off 12V and the Arduino uno has the ability to be powered by a wide range of voltages.
NOTE: If any kind of Arduino is used, that does not have an on board voltage regulator, you will need to bump down the voltage to 5V yourself, before powering on the board. Something like a 7805 voltage regulator can be used here.
Pin 3 and 5 connects to the PWM pins on the fans. These pins are used as they allow for PWM signals to be used, which is basically rapid 1s and 0s, which controls how fast the fans spin.
Pin A0 is used as the input for the potentiometer. The potentiometers other two pins are connected to GND and +5V, meaning that it works as a variable voltage divider. The voltage on the middle pin will therefore be somewhere between 0 and 5V depending on the position. The Arduino can read this value on it's analog pins, and the value is being translated in code to a percentage, as well as a PWM signal to be output on pin 3.
Step 2: Building the Box
We chose to lasercut all the pieces to make a nice enclosure for our project. Attached is the original Illustrator file we drew up, so anyone can replicate or modify it. We chose to make ours out of wood as that would match the color of the fans, but any kind of material can be used as long as it has a thickness of 4mm.
Step 3: More Pictures of the Box Assembly
Here are more pictures that show how the box goes together. Notice how the cuts in the front as well as the fan guard behind it are horizontal. This was done to prevent the flexible sheet of carbon filter to get stuck in the fan when inserting it into the slot.
The sides all snap together by cut out "fingers". The bottom of the case can be attached by screws so you it's possible to reach the parts inside and make further modifications. The Arduino is stuck to the bottom plate.
Step 4: Update With LCD
While we didn't get the OLED display we ordered, we tried hooking up an old school LCD to display the speed of the main fan.